What is Life?

What do you classify as being living?

Is a virus living?

Why not? it reproduces, & gets energy right?

In order to be considered living you need to be able to get energy & reproduce.

There are 2 theories. 

The most commonly known is the CELL THEORY. 

In the CELL THEORY it says that all living cells come from other pre-existing cells & that all living things are composed of cells.

Another theory is the STAR STUFF theory in which all living things come from things brought from outer space.                                                                                                                                          

They are all also made of organic compounds.

There are 4 organic compounds---

1. Lipids- store energy
   
2. Carbs- are the main source of energy
   
3. Nucleic Acids- contain genetic information needed to reproduce and get energy
   
4. Proteins- help produce enzymes to speed up chemical reactions in your body.

The WATER Molecule

• is held together by hydrogen bonds
• cohesion is the attraction between substances
• adhesion is the attraction between different substances
• A mixture is made of 2 elements or more
• A solution is an even distribution of substances in a mixture
• A suspension is non dissolved, not even distrubution of substances in a mixture

Chemical Bonds

• There are 2 types of bonds
  

1. Covelant bonds- share atoms to form molecules- molecules are the smallest units in compounds.- 
2. ionic bonds- share ions that can be (+) or (-) charged. its (-) when it adds an electron and when it looses one it becomes (+)

Elements

• there are over 180 elements known
• 92 of them are natural

Chemical Reactions

• Enzymes are proteins used to speed up chemical reactions.
• They are specific to the reaction they can speed up.